Coupling wide memory interface to wide write back paths

ABSTRACT

Systems and methods are disclosed for performing wide memory operations for a wide data cache line. In some examples of the disclosed technology, a processor having two or more execution lanes includes a data cache coupled to memory, a wide memory load circuit that concurrently loads two or more words from a cache line of the data cache, and a writeback circuit situated to send a respective word of the concurrently-loaded words to a selected execution lane of the processor, either into an operand buffer or bypassing the operand buffer. In some examples, a sharding circuit is provided that allows bitwise, byte-wise, and/or word-wise manipulation of memory operation data. In some examples, wide cache loads allows for concurrent execution of plural execution lanes of the processor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional Application No.62/624,067, filed Jan. 30, 2018, which application is incorporated byreference in its entirety.

BACKGROUND

Microprocessors have benefited from continuing gains in transistorcount, integrated circuit cost, manufacturing capital, clock frequency,and energy efficiency due to continued transistor scaling predicted byMoore's law, with little change in associated processor Instruction SetArchitectures (ISAs). However, the benefits realized fromphotolithographic scaling, which drove the semiconductor industry overthe last 40 years, are slowing or even reversing. Reduced InstructionSet Computing (RISC) architectures have been the dominant paradigm inprocessor design for many years. Out-of-order superscalarimplementations have not exhibited sustained improvement in area orperformance. Accordingly, there is ample opportunity for improvements inprocessor ISAs to extend performance improvements.

SUMMARY

Methods, apparatus, and computer-readable storage devices are disclosedfor processors, including those having a general purpose instruction setarchitecture (ISA), such as RISC or Complex Instruction Set Computing(CISC) ISAs, block-based processor instruction set architecture(BB-ISA), or other ISAs. These microarchitectures can be configured toexecute instructions using a variable number of allocated resources.

The described techniques and tools can potentially improve processorperformance and can be implemented separately, or in variouscombinations with each other. As will be described more fully below, thedescribed techniques and tools can be implemented in a digital signalprocessor, microprocessor, application-specific integrated circuit(ASIC), a soft processor (e.g., a microprocessor core implemented in afield programmable gate array (FPGA) using reconfigurable logic),programmable logic, or other suitable logic circuitry. As will bereadily apparent to one of ordinary skill in the art, the disclosedtechnology can be implemented in various computing platforms, including,but not limited to, servers, mainframes, cellphones, smartphones, PDAs,handheld devices, handheld computers, touch screen tablet devices,tablet computers, wearable computers, and laptop computers. Thedisclosed techniques can be used in general-purpose Reduced InstructionSet Computing (RISC) or Complex Instruction Set Computing (CISC)processors, block based processors such as Explicit Data Graph Execution(EDGE) processors, digital signal processors, or other suitable types ofprocessors.

In some examples of the disclosed technology, an apparatus comprising aprocessor having two or more execution lanes includes a data cachecoupled to memory, a wide memory load circuit that concurrently loadstwo or more words from a cache line of the data cache, and a write backpath situated to send the respective selected word of the concurrentlyloaded words from the cache line to a respective selected execution laneof the processor. In some examples, the apparatus can be configured toperform methods of rearranging words, bytes, and/or bits of the loadeddata and/or storage data using a sharding circuit. In some examples, atleast some of the operations performed with the execution lanes includesSIMD operations on portions of a word or byte.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. The foregoingand other objects, features, and advantages of the disclosed subjectmatter will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block-based processor including multiple processorcores, as can be used in some examples of the disclosed technology.

FIG. 2 illustrates a block-based processor core, as can be used in someexamples of the disclosed technology.

FIG. 3 illustrates a number of instruction blocks, according to certainexamples of disclosed technology.

FIG. 4 illustrates portions of source code and respective instructionblocks.

FIG. 5 illustrates block-based processor headers and instructions, ascan be used in some examples of the disclosed technology.

FIG. 6 is a flowchart illustrating an example of a progression of statesof a processor core of a block-based processor.

FIG. 7 is a block diagram illustrating an example data path having awriteback circuit and a sharding circuit, as can be implemented incertain examples of the disclosed technology.

FIG. 8 is a block diagram illustrating an example data path having abyte-wise sharding circuit, as can be implemented in certain examples ofthe disclosed technology.

FIG. 9 is a block diagram illustrating an example data path having abypass writeback path controlled by a leader instruction window, as canbe implemented in certain examples of the disclosed technology.

FIG. 10 is a block diagram illustrating an example data path havingfewer execution units than execution lanes, as can be implemented incertain examples of the disclosed technology.

FIGS. 11A-C illustrate a method of performing a multiply-reduceoperation, as can be performed in certain examples of the disclosedtechnology.

FIG. 12 is a block diagram illustrating an example data path showingalternative locations of a sharding circuit, as can be implemented incertain examples of the disclosed technology.

FIG. 13 is a flow chart outlining an example method of sending data froma wide cache line, as can be performed in certain examples of thedisclosed technology.

FIG. 14 is a flow chart outlining an example method of sending data froma cache line to an operand buffer, or bypassing the operand buffer, ascan be performed in certain examples of the disclosed technology.

FIG. 15 is a flow chart outlining an example method of schedulingoperations for two or more execution lanes and performing memoryoperations, as can be performed in certain examples of the disclosedtechnology.

FIGS. 16A and 16B depict source and assembly code for a matrix vectormultiplication inner loop, as can be used in certain examples of thedisclosed technology.

FIGS. 17A-17C depict source and assembly code for a re-factored matrixvector multiplication inner loop, as can be used in certain examples ofthe disclosed technology.

FIGS. 18A and 18B illustrate scheduled operations to perform a matrixvector multiplication inner loop, as can be used in certain examples ofthe disclosed technology.

FIG. 19 is a block diagram illustrating a suitable computing environmentfor implementing some embodiments of the disclosed technology.

DETAILED DESCRIPTION

I. General Considerations

This disclosure is set forth in the context of representativeembodiments that are not intended to be limiting in any way.

As used in this application the singular forms “a,” “an,” and “the”include the plural forms unless the context clearly dictates otherwise.Additionally, the term “includes” means “comprises.” Further, the term“coupled” encompasses mechanical, electrical, magnetic, optical, as wellas other practical ways of coupling or linking items together, and doesnot exclude the presence of intermediate elements between the coupleditems. Furthermore, as used herein, the term “and/or” means any one itemor combination of items in the phrase.

The systems, methods, and apparatus described herein should not beconstrued as being limiting in any way. Instead, this disclosure isdirected toward all novel and non-obvious features and aspects of thevarious disclosed embodiments, alone and in various combinations andsubcombinations with one another. The disclosed systems, methods, andapparatus are not limited to any specific aspect or feature orcombinations thereof, nor do the disclosed things and methods requirethat any one or more specific advantages be present or problems besolved. Furthermore, any features or aspects of the disclosedembodiments can be used in various combinations and subcombinations withone another.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthbelow. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed things and methods can be used in conjunction with otherthings and methods. Additionally, the description sometimes uses termslike “produce,” “generate,” “display,” “receive,” “emit,” “verify,”“execute,” and “initiate” to describe the disclosed methods. These termsare high-level descriptions of the actual operations that are performed.The actual operations that correspond to these terms will vary dependingon the particular implementation and are readily discernible by one ofordinary skill in the art.

As used herein, “bit” means a basic unit of data for a processor. A bitis typically either a zero (0) or one (1), but in certain architectures,ternary or other non-binary bits can be employed. As used herein, theterm “word” refers to a unit of two or more bits of data that is thesize of an instruction operand. Words are typically 16, 32, 64, or 128bits, although other sizes of words, including 48, 80, or 256 bits canbe used. In certain applications, smaller words (e.g., 4-bit, 6-bit, or8-bit) words may be used, including some neural network or low-precisionapplications. As used herein, “bytes” are typically 7 or 8 bits.

Theories of operation, scientific principles, or other theoreticaldescriptions presented herein in reference to the apparatus or methodsof this disclosure have been provided for the purposes of betterunderstanding and are not intended to be limiting in scope. Theapparatus and methods in the appended claims are not limited to thoseapparatus and methods that function in the manner described by suchtheories of operation.

Any of the disclosed methods can be implemented as computer-executableinstructions stored on one or more computer-readable media (e.g.,computer-readable media, such as one or more optical media discs,volatile memory components (such as DRAM or SRAM), or nonvolatile memorycomponents (such as hard drives)) and executed on a computer (e.g., anycommercially available computer, including smart phones or other mobiledevices that include computing hardware). Any of the computer-executableinstructions for implementing the disclosed techniques, as well as anydata created and used during implementation of the disclosedembodiments, can be stored on one or more computer-readable media (e.g.,computer-readable storage media). The computer-executable instructionscan be part of, for example, a dedicated software application or asoftware application that is accessed or downloaded via a web browser orother software application (such as a remote computing application).Such software can be executed, for example, on a single local computer(e.g., with general-purpose and/or block-based processors executing onany suitable commercially available computer) or in a networkenvironment (e.g., via the Internet, a wide-area network, a local-areanetwork, a client-server network (such as a cloud computing network), orother such network) using one or more network computers.

For clarity, only certain selected aspects of the software-basedimplementations are described. Other details that are well known in theart are omitted. For example, it should be understood that the disclosedtechnology is not limited to any specific computer language or program.For instance, the disclosed technology can be implemented by softwarewritten in C, C++, Java, or any other suitable programming language.Likewise, the disclosed technology is not limited to any particularcomputer or type of hardware. Certain details of suitable computers andhardware are well-known and need not be set forth in detail in thisdisclosure.

Furthermore, any of the software-based embodiments (comprising, forexample, computer-executable instructions for causing a computer toperform any of the disclosed methods) can be uploaded, downloaded, orremotely accessed through a suitable communication means. Such suitablecommunication means include, for example, the Internet, the World WideWeb, an intranet, software applications, cable (including fiber opticcable), magnetic communications, electromagnetic communications(including RF, microwave, and infrared communications), electroniccommunications, or other such communication means.

II. Introduction to the Disclosed Technologies

Superscalar out-of-order microarchitectures employ substantial circuitresources to rename registers, schedule instructions in dataflow order,clean up after miss-speculation, and retire results in-order for preciseexceptions. This includes expensive energy-consuming circuits, such asdeep, many-ported register files, many-ported content-accessiblememories (CAMs) for dataflow instruction scheduling wakeup, andmany-wide bus multiplexers and bypass networks, all of which areresource intensive. For example, FPGA-based implementations ofmulti-read, multi-write RAMs typically require a mix of replication,multi-cycle operation, clock doubling, bank interleaving, live-valuetables, and other expensive techniques. Further, implementations ofcertain high memory bandwidth operations, such as neural networks, istypically inefficient using general purpose architectures.

The disclosed technologies can realize energy efficiency and/orperformance enhancement through application of techniques including highinstruction-level parallelism (ILP), out-of-order (OoO), superscalarexecution, while avoiding substantial complexity and overhead in bothprocessor hardware and associated software. In some examples of thedisclosed technology, a block-based processor comprising multipleprocessor cores uses an Explicit Data Graph Execution (EDGE) ISAdesigned for area- and energy-efficient, high-ILP execution. In someexamples, a general purpose instruction set architecture (ISA), such asRISC or Complex Instruction Set Computing (CISC) ISA processor isadapted to use the wide memory load circuits, writeback circuits, and/orsharding circuit disclosed herein. In some examples, use of EDGEarchitectures and associated compilers finesses away much of theregister renaming, CAMs, and complexity. In some examples, therespective cores of the block-based processor can store or cache fetchedand decoded instructions that may be repeatedly executed, and thefetched and decoded instructions can be reused to potentially achievereduced power and/or increased performance.

In certain examples of the disclosed technology, an EDGE ISA caneliminate the need for one or more complex architectural features,including register renaming, dataflow analysis, misspeculation recovery,and in-order retirement while supporting mainstream programminglanguages such as C and C++. In certain examples of the disclosedtechnology, a block-based processor executes a plurality of two or moreinstructions as an atomic block. Block-based instructions can be used toexpress semantics of program data flow and/or instruction flow in a moreexplicit fashion, allowing for improved compiler and processorperformance. In certain examples of the disclosed technology, anexplicit data graph execution instruction set architecture (EDGE ISA)includes information about program control flow that can be used toimprove detection of improper control flow instructions, therebyincreasing performance, saving memory resources, and/or and savingenergy.

In some block-based examples of the disclosed technology, instructionsorganized within instruction blocks are fetched, executed, and committedatomically. Within an instruction block, instructions directlycommunicate results to consuming instructions through operand buffers.Across blocks, results are communicated through named registers.Intermediate results produced by the instructions within an atomicinstruction block that affect the architectural state are bufferedlocally until the instruction block is committed. When the instructionblock is committed, updates to the visible architectural state resultingfrom executing the instructions of the instruction block are madevisible to other instruction blocks. Instructions inside blocks executein dataflow order, which reduces or eliminates using register renamingand provides power-efficient OoO execution. In current processtechnologies, a typical BB-ISA design may support up to 128-instructionblocks. The block size can influence processor performance, but ingeneral, larger blocks up to a certain size (e.g., 128- or 256-wordblocks) are preferred using current process technologies. A program'scharacteristics, among other factors, can influence the optimuminstruction block size.

A compiler can be used to explicitly encode data dependencies throughthe ISA, reducing or eliminating burdening processor core control logicfrom rediscovering dependencies at runtime. This includes detection ofopportunities to perform wide, multi-word or multi-byte load and storememory operations. In examples using predicated execution, intra-blockbranches can be converted to dataflow instructions, and dependencies,other than memory dependencies, can be limited to direct datadependencies. Disclosed target form encoding techniques allowinstructions within a block to communicate their operands directly viaoperand buffers, reducing accesses to a power-hungry, multi-portedphysical register files.

Between instruction blocks, instructions can communicate using visiblearchitectural state such as memory and registers. Thus, by utilizing ahybrid dataflow execution model, EDGE architectures can still supportimperative programming languages and sequential memory semantics, butdesirably also enjoy the benefits of out-of-order execution with nearin-order power efficiency and complexity.

In some examples, memory can be loaded or stored speculatively. Forexample, a memory load/store queue can be used to route memory accessperformed by instructions, thereby minimizing delays in fetching andstoring data in memory. In some examples, instruction-level parallelismcan be exploited to execute multiple instructions within a block inparallel. In some examples of the disclosed technology, a BB-ISA exposesdetails of instruction block size and load-store queue size to theprogrammer, allowing for improved optimization (by a manual programmeror by a compiler).

As will be readily understood to one of ordinary skill in the relevantart, a spectrum of implementations of the disclosed technology arepossible with various area, performance, and power tradeoffs.

III. Example Processor

FIG. 1 is a block diagram 10 of a multi-core processor 100 as can beimplemented in some examples of the disclosed technology. The processor100 is configured to execute blocks of instructions according to aninstruction set architecture (ISA), which describes a number of aspectsof processor operation, including a register model, a number of definedoperations performed by instructions, a memory model, interrupts, andother architectural features. The processor includes a plurality ofprocessing cores 110, including a processor core 111. The processor 100can implement an EDGE ISA, a RISC ISA, a CISC ISA, a DSP ISA, and/or anyother suitable instruction set.

As shown in FIG. 1, the processor cores are connected to each other viacore interconnect 120. The core interconnect 120 carries data andcontrol signals between individual ones of the cores 110, a memoryinterface 140, and an input/output (I/O) interface 145. The coreinterconnect 120 can transmit and receive signals using electrical,optical, magnetic, or other suitable communication technology and canprovide communication connections arranged according to a number ofdifferent topologies, depending on a particular desired configuration.For example, the core interconnect 120 can have a crossbar, a bus, apoint-to-point bus, or other suitable topology. In some examples, anyone of the cores 110 can be connected to any of the other cores, whilein other examples, some cores are only connected to a subset of theother cores. For example, each core may only be connected to a nearest4, 8, or 20 neighboring cores. The core interconnect 120 can be used totransmit input/output data to and from the cores, as well as transmitcontrol signals and other information signals to and from the cores. Forexample, each of the cores 110 can receive and transmit semaphores thatindicate the execution status of instructions currently being executedby each of the respective cores. In some examples, the core interconnect120 is implemented as wires connecting the cores 110, and memory system,while in other examples, the core interconnect can include circuitry formultiplexing data signals on the interconnect wire(s), switch and/orrouting components, including active signal drivers and repeaters, orother suitable circuitry. In some examples of the disclosed technology,signals transmitted within and to/from the processor 100 are not limitedto full swing electrical digital signals, but the processor can beconfigured to include differential signals, pulsed signals, or othersuitable signals for transmitting data and control signals.

In the example of FIG. 1, the memory interface 140 of the processorincludes interface logic that is used to connect to additional memory,for example, memory located on another integrated circuit besides theprocessor 100. As shown in FIG. 1 an external memory system 150 includesan L2 cache 152 and main memory 155. In some examples the L2 cache canbe implemented using static RAM (SRAM) and the main memory 155 can beimplemented using dynamic RAM (DRAM). In some examples the memory system150 is included on the same integrated circuit as the other componentsof the processor 100. In some examples, the memory interface 140includes a direct memory access (DMA) controller allowing transfer ofblocks of data in memory without using register file(s) and/or theprocessor 100. In some examples, the memory interface 140 can include amemory management unit (MMU) for managing and allocating virtual memory,expanding the available main memory 155.

The I/O interface 145 includes circuitry for receiving and sending inputand output signals to other components, such as hardware interrupts,system control signals, peripheral interfaces, co-processor controland/or data signals (e.g., signals for a graphics processing unit,floating point coprocessor, physics processing unit, digital signalprocessor, or other co-processing components), clock signals,semaphores, or other suitable I/O signals. The I/O signals may besynchronous or asynchronous. In some examples, all or a portion of theI/O interface 145 is implemented using memory-mapped I/O techniques inconjunction with the memory interface 140.

The processor 100 can also include a control unit 160. The control unitcan communicate with the processing cores 110, the I/O interface 145,and the memory interface 140 via the core interconnect 120 or aside-band interconnect (not shown). The control unit 160 supervisesoperation of the processor 100. Operations that can be performed by thecontrol unit 160 can include allocation and de-allocation of cores forperforming instruction processing, control of input data and output databetween any of the cores, register files, the memory interface 140,and/or the I/O interface 145, modification of execution flow, andverifying target location(s) of branch instructions, instructionheaders, and other changes in control flow. The control unit 160 canalso process hardware interrupts, and control reading and writing ofspecial system registers, for example the program counter (or aninstruction block address register) stored in one or more registerfile(s). In some examples of the disclosed technology, the control unit160 is at least partially implemented using one or more of theprocessing cores 110, while in other examples, the control unit 160 isimplemented using a non-block-based processing core (e.g., ageneral-purpose RISC processing core coupled to memory). In someexamples, the control unit 160 is implemented at least in part using oneor more of: hardwired finite state machines, programmable microcode,programmable gate arrays, or other suitable control circuits. Inalternative examples, control unit functionality can be performed by oneor more of the cores 110.

The control unit 160 includes a scheduler that is used to allocateinstruction blocks to the processor cores 110. As used herein, schedulerallocation refers to hardware for directing operation of instructionblocks, including initiating instruction block mapping, fetching,decoding, execution, committing, aborting, idling, and refreshing aninstruction block. In some examples, the hardware receives signalsgenerated using computer-executable instructions to direct operation ofthe instruction scheduler. Processor cores 110 are assigned toinstruction blocks during instruction block mapping. The recited stagesof instruction operation are for illustrative purposes, and in someexamples of the disclosed technology, certain operations can becombined, omitted, separated into multiple operations, or additionaloperations added. The control unit 160 can further be used to allocatedfunctional resources within the processor cores to contexts. Forexample, instruction cache, instruction windows, functional units,register files, branch predictors (next block predictors), and/or datacache can be allocated by the control unit 160.

The processor 100 also includes a clock generator 170, which distributesone or more clock signals to various components within the processor(e.g., the cores 110, interconnect 120, memory interface 140, and I/Ointerface 145). In some examples of the disclosed technology, all of thecomponents share a common clock, while in other examples differentcomponents use a different clock, for example, a clock signal havingdiffering clock frequencies. In some examples, a portion of the clock isgated to allow power savings when some of the processor components arenot in use. In some examples, the clock signals are generated using aphase-locked loop (PLL) to generate a signal of fixed, constantfrequency and duty cycle. Circuitry that receives the clock signals canbe triggered on a single edge (e.g., a rising edge) while in otherexamples, at least some of the receiving circuitry is triggered byrising and falling clock edges. In some examples, the clock signal canbe transmitted optically or wirelessly.

IV. Example Processor Core

FIG. 2 is a block diagram further detailing an example microarchitecture200 for implementing the processor 100, and in particular, an instanceof one of the processor cores, as can be used in certain examples of thedisclosed technology. The core can execute a general purpose instructionset architecture (ISA), such as RISC or Complex Instruction SetComputing (CISC) ISAs, block-based processor instruction setarchitecture (BB-ISA), a digital signal processor (DSP), or othersuitable ISA. For ease of explanation, the exemplary microarchitecturehas five pipeline stages including: instruction fetch (IF), decode (DC),issue, including operand fetch (IS), execute (EX), and memory/dataaccess (LS). However, it will be readily understood by one of ordinaryskill in the relevant art that modifications to the illustratedmicroarchitecture, such as adding/removing stages, adding/removing unitsthat perform operations, and other implementation details can bemodified to suit a particular application for a block-based processor.

As shown in FIG. 2, the processor core includes an instruction cache 210that is coupled to an instruction decoder 220. The instruction cache 210is configured to receive processor instructions from a memory. In someFPGA implementations, the instruction cache can be implemented by a dualread port, dual write port, 18 or 36 Kb (kilobit), 32 bit wide blockRAM. In some examples, the physical block RAM is configured to operateas two or more smaller block RAMs.

The processor core further includes an instruction window 230, whichincludes an instruction scheduler 235, a decoded instruction store 236,and a plurality of operand buffers 239. In FPGA implementations, each ofthese instruction window components 230 can be implemented including theuse of LUT RAM (e.g., with SRAM configured as lookup tables) or BRAM(block RAM).

In block-based examples, the instruction scheduler 235 can send aninstruction identifier (instruction ID or IID) for an instruction to thedecoded instruction store 236 and the operand buffers 239 as a controlsignal. As discussed further below, each instruction in an instructionblock has an associated instruction identifier that uniquely identifiesthe instruction within the instruction block. In some examples,instruction targets for sending the result of executing an instructionare encoded in the instruction. In this way, dependencies betweeninstructions can be tracked using the instruction identifier instead ofmonitoring register dependencies, as typically used in RISC and CISCgeneral-purpose processors. In some examples, the processor core caninclude two or more instruction windows. In some examples, the processorcore can include one instruction window with multiple block contexts.

As will be discussed further below, the microarchitecture 200 includes aregister file 290 that stores data for registers defined in theprocessor architecture, and can have one or more read ports and one ormore write ports. In block-based processor examples, because aninstruction block executes on a transactional basis, changes to registervalues made by an instance of an instruction block are not visible tothe same instance; the register writes will be committed upon completingexecution of the instruction block.

The decoded instruction store 236 stores decoded signals for controllingoperation of hardware components in the processor pipeline. For example,a 32-bit instruction may be decoded into 128-bits of decoded instructiondata. The decoded instruction data is generated by the decoder 220 afteran instruction is fetched. The operand buffers 239 store operands (e.g.,register values received from the register file, data received frommemory, immediate operands coded within an instruction, operandscalculated by an earlier-issued instruction, or other operand values)until their respective decoded instructions are ready to execute.Instruction operands and predicates for the execute phase of thepipeline are read from the operand buffers 239, respectively, not(directly, at least) from the register file 290. The instruction window230 can include a buffer for predicates directed to an instruction,including wired-OR logic for combining predicates sent to an instructionby multiple instructions.

In some examples, all of the instruction operands, except for registerread operations, are read from the operand buffers 239 instead of theregister file. In some examples the values are maintained until theinstruction issues and the operand is communicated to the executionpipeline. In some FPGA examples, the decoded instruction store 236 andoperand buffers 239 are implemented with a plurality of LUT RAMs.

The instruction scheduler 235 maintains a record of ready state of eachdecoded instruction's dependencies (e.g., the instruction's predicateand data operands). When all of the instruction's dependencies (if any)are satisfied, the instruction wakes up and is ready to issue.Attributes of the instruction window 230 and instruction scheduler 235,such as area, clock period, and capabilities can have significant impactto the realized performance of an EDGE core and the throughput of anEDGE multiprocessor. In some examples, the front end (IF, DC) portionsof the microarchitecture can run decoupled from the back end portions ofthe microarchitecture (IS, EX, LS). In some FPGA implementations, theinstruction window 230 is configured to fetch and decode twoinstructions per clock into the instruction window.

Control circuits (e.g., signals generated using the decoded instructionstore 236) in the instruction window 230 are used to generate controlsignals to regulate core operation (including, e.g., control of datapathand multiplexer select signals) and to schedule the flow of instructionswithin the core. This can include generating and using memory accessinstruction encodings, allocation and de-allocation of cores forperforming instruction processing, control of input data and output databetween any of the cores 110, register files, the memory interface 140,and/or the I/O interface 145.

In some examples, the instruction scheduler 235 is implemented as afinite state machine coupled to other instruction window logic. In someexamples, the instruction scheduler is mapped to one or more banks ofRAM in an FPGA, and can be implemented with block RAM, LUT RAM, or otherreconfigurable RAM. As will be readily apparent to one of ordinary skillin the relevant art, other circuit structures, implemented in anintegrated circuit, programmable logic, or other suitable logic can beused to implement hardware for the instruction scheduler 235. In someexamples of the disclosed technology, front-end pipeline stages IF andDC can run decoupled from the back-end pipelines stages (IS, EX, LS).

In the example of FIG. 2, the operand buffers 239 send the data operandsto a set of execution state pipeline registers 245 via one or moreswitches (e.g., multiplexers 241 and 242). In block-based examples,these be designated left operand (LOP) and right operand (ROP) or alsobe referred to as OP1 and OP0, respectively. A first router 240 is usedto send data from the operand buffers 239 to one or more of thefunctional units 250, which can include but are not limited to, integerALUs (arithmetic logic units) (e.g., integer ALUs 255), floating pointunits (e.g., floating point ALU 256), shift/rotate logic (e.g., barrelshifter 257), or other suitable execution units, which can includinggraphics functions, physics functions, and other mathematicaloperations. In some examples, an additional programmable execution unit(not shown) can be reconfigured to implement a number of differentarbitrary functions (e.g., a priori or at runtime).

Data from the functional units 250 can then be routed through a secondrouter (not shown) to a set of load/store pipeline registers 260, to aload/store queue 270 (e.g., for performing memory load and memory storeoperations), or fed back to the execution pipeline registers, therebybypassing the operand buffers 239. The load/store queue 270 is coupledto a data cache 275 that caches data for memory operations, includingwide data cache line loads and stores. The outputs of the data cache 275and the load/store pipelines registers 260 can be sent to a third router280, which in turn sends data to the register file 290, the operandbuffers 239, and/or the execution pipeline registers 245, according tothe instruction being executed in the pipeline stage.

A sharding circuit 277 can be used to perform bitwise, byte-wise, ormulti-byte-wise data manipulations, as will be further discussed below.Some implementations use an arrangement as shown in FIG. 2. However, inother examples, the sharding circuit 277 can be placed in otherarrangements, such as the two arrangements indicated by dashed lines inFIG. 2.

In block-based processor implementations, when execution of aninstruction block is complete, the instruction block is designated as“committed” and signals from the control outputs can in turn can be usedby other cores within the block-based processor 100 and/or by thecontrol unit 160 to initiate scheduling, fetching, and execution ofother instruction blocks.

As will be readily understood to one of ordinary skill in the relevantart, the components within an individual core are not limited to thoseshown in FIG. 2, but can be varied according to the requirements of aparticular application. For example, a core may have fewer or moreinstruction windows, a single instruction decoder might be shared by twoor more instruction windows, and the number of and type of functionalunits used can be varied, depending on the particular targetedapplication for the block-based processor. Other considerations thatapply in selecting and allocating resources with an instruction coreinclude performance requirements, energy usage requirements, integratedcircuit die, process technology, and/or cost.

As will be readily apparent to one of ordinary skill in the relevant arthaving the benefit of the present disclosure, trade-offs can be made inprocessor performance by the design and allocation of resources withinthe instruction window and control unit of the processor cores 110. Thearea, clock period, capabilities, and limitations substantiallydetermine the realized performance of the individual cores 110 and thethroughput of the block-based processor 100.

In block-based processor implementations, changes to the visiblearchitectural state of the processor (such as to the register file 290and the memory) affected by the executed instructions can be bufferedlocally within the core until the instructions are committed. Thecontrol circuitry can determine when instructions are ready to becommitted, sequence the commit logic, and issue a commit signal. Forexample, a commit phase for an instruction block can begin when allregister writes are buffered, all writes to memory (includingunconditional and conditional stores) are buffered, and a branch targetis calculated. The instruction block can be committed when updates tothe visible architectural state are complete. For example, aninstruction block can be committed when the register writes are writtento as the register file, the stores are sent to a load/store unit ormemory controller, and the commit signal is generated. The controlcircuit also controls, at least in part, allocation of functional unitsto the instructions window.

Because the instruction block is committed (or aborted) in block-basedprocessor implementations as an atomic transactional unit, it should benoted that results of certain operations are not available toinstructions within an instruction block. This is in contrast to RISCand CISC architectures that provide results visible on an individual,instruction-by-instruction basis. Thus, additional techniques aredisclosed for supporting memory synchronization and other memoryoperations in a block-based processor environment.

In some examples, non-control flow instructions (e.g., instructions thatare not branch or jump instructions, which can update a program counter)can be non-predicated, or predicated true or false. A predicatedinstruction does not become ready until it is targeted by anotherinstruction's predicate result, and that result matches the predicatecondition. If the instruction's predicate does not match, then theinstruction never issues.

In some examples, upon branching to a new instruction block, allinstruction window ready state (stored in the instruction scheduler 235)is flash cleared (block reset). However when a block branches back toitself (block refresh), only active ready state is cleared; the decodedready state is preserved so that it is not necessary to re-fetch anddecode the blocks instructions. Thus, refresh can be used to save timeand energy in loops, instead of performing a block reset. It can beespecially advantageous in certain wide memory load applications toavoid re-fetching instructions for a large number of instructionwindows. In some examples, instruction lanes execute lock-step with aleader instruction window, further improving efficiency.

A number of different technologies can be used to implement theinstruction scheduler 235. For example, the scheduler 235 can beimplemented as a parallel scheduler, where instructions' ready state isexplicitly represented in FPGA D-type flip-flops (FFs), and in which theready status of every instruction is reevaluated each cycle. In otherexamples, the instruction scheduler 235 can be implemented as a morecompact incremental scheduler that keeps ready state in LUT RAM andwhich updates ready status of about two to four target instructions percycle.

The register file 290 may include two or more write ports for storingdata in the register file, as well as having a plurality of read portsfor reading data from individual registers within the register file. Insome examples, a single instruction window (e.g., instruction window230) can access only one port of the register file at a time, while inother examples, the instruction window 230 can access one read port andone write port, or can access two or more read ports and/or write portssimultaneously. In some examples, the microarchitecture is configuredsuch that not all the read ports of the register 290 can use the bypassmechanism.

In some examples, the register file 290 can include 64 registers, eachof the registers holding a word of 32 bits of data. (For convenientexplanation, this application will refer to 32-bits of data as a word,unless otherwise specified. Suitable processors according to thedisclosed technology could operate with 8-, 16-, 64-, 128-, 256-bit, oranother number of bits words) In some examples, some of the registerswithin the register file 290 may be allocated to special purposes. Forexample, some of the registers can be dedicated as system registersexamples of which include registers storing constant values (e.g., anall zero word), program counter(s) (PC), which indicate the currentaddress of a program thread that is being executed, a physical corenumber, a logical core number, a core assignment topology, core controlflags, execution flags, a processor topology, or other suitablededicated purpose. In some examples, the register file 290 isimplemented as an array of flip-flops, while in other examples, theregister file can be implemented using latches, SRAM, or other forms ofmemory storage. The ISA specification for a given processor specifieshow registers within the register file 290 are defined and used.

In block-based processor examples, the registers store architecturalstate, which can be passed to and from different instruction blocks. Thearchitectural state registers are defined by the processor's instructionset architecture. Because the register file is architecturally visibleto the programmer, each concurrently executing context (e.g., a threador process) is allocated its own register file, or its own portion ofthe architectural register file. In some examples, this can beimplemented by providing a separate register file for each context, orby using a single register file large enough to accommodate every activecontext, but having appropriate partitions. Any suitable storagetechnology can be used to implement the architectural register file,including the use of storage elements formed from flip-flops andlatches, static RAM (SRAM), or other suitable memory technology. Theregister file 290 can be formed from a portion or all of a physicalregister file, which is an array of registers formed from storageelements, that is not necessarily restricted to the processor ISA. Forexample, physical register files can be partitioned to form multiplearchitectural register files, each of which is associated with aparticular context. In some examples, the physical register may beconfigured to store renamed register values, or to store register valuesfor a speculatively executed thread or process. Physical register filescan be formed from similar storage elements, including flip-flops andlatches, static RAM (SRAM), or other suitable memory technology. Suchregister files can also have multiple input ports and/or multiple readports in certain implementations.

V. Example Stream of Block-Based Instruction Blocks

Turning now to the diagram 300 of FIG. 3, a portion 310 of a stream ofblock-based instructions, including a number of variable lengthinstruction blocks 311-315 (A-E) is illustrated. The stream ofinstructions can be used to implement user application, system services,or any other suitable use. In the example shown in FIG. 3, eachinstruction block begins with an instruction header, which is followedby a varying number of instructions. For example, the “A” instructionblock 311 includes a four-word header 320 and seventy instructions 321.In some examples, an instruction block is divided or “folded” to fitinto resources that have been allocated for executing the instructionblock. For example, a block-based processor according to the disclosedtechnology may include instruction windows configured to track state andexecute instructions in 32-word chunks. Thus, the A instruction block311 can be divided into three portions. These portions may be allocatedto three segments (or “execution lanes”), or results from the firstinstruction block portion can be temporarily stored in a results bufferbefore passing to the subsequent, second portion of the instructionblock. Similarly, the “B” instruction block 312 is a 64-word instructionblock that can be divided into two, 32-word portions 330, and the “E”instruction block 315 is a 128-word instruction block that can bedivided into four, 32-word portions 340. As will be readily understoodto one of ordinary skill in the art having the benefit of the presentdisclosure, instruction blocks may be divided into different sizeportions, depending on resources in a particular implementation.Further, compilers adapted to generate machine instructions fordisclosed processors can arrange instructions within an instructionblock to improve processor performance, by, for example, allocatinginstructions to fall within certain portions of an instruction block. Inother configurations, processor resources can be combined such that theinstruction block (e.g., instruction block 311 or 315) is fetched andexecuted as a single instruction block. In some examples, a processoraccording to the disclosed technologies can be re-configured to operatein two or more different such modes.

The particular, exemplary instruction header 320 illustrated includes anumber of data fields that control, in part, execution of theinstructions within the instruction block, and also allow for improvedperformance enhancement techniques including, for example branchprediction, speculative execution, lazy evaluation, and/or othertechniques. The instruction header 320 also includes an ID bit whichindicates that the header is an instruction header and not aninstruction. The instruction header 320 also includes an indication ofthe instruction block size. The instruction block size can be in largerchunks of instructions than one, for example, the number of4-instruction chunks contained within the instruction block. In otherwords, the size of the block is shifted 4 bits in order to compressheader space allocated to specifying instruction block size. Thus, asize value of 0 (zero) indicates a minimally-sized instruction blockwhich is a block header followed by four instructions. In some examples,the instruction block size is expressed as a number of bytes, as anumber of words, as a number of n-word chunks, as an address, as anaddress offset, or using other suitable expressions for describing thesize of instruction blocks. In some examples, the instruction block sizeis indicated by a terminating bit pattern in the instruction blockheader and/or footer.

The instruction block header 320 can also include execution flags, whichindicate special instruction execution requirements. For example,indication of “leader” instruction blocks, specification of wide memoryloads, sharing operations, or other suitable execution requirements canbe specified in the instruction block header 320. The instruction blockheader 320 can also indicate branch prediction or memory dependenceprediction can be inhibited for certain instruction blocks, depending onthe particular application. As another example, an execution flag can beused to control whether the instruction block is executed in the defaultexecution mode or the debug execution mode.

In some examples of the disclosed technology, the instruction header 320includes one or more identification bits that indicate that the encodeddata is an instruction header. For example, in some block-basedprocessor ISAs, a single ID bit in the least significant bit space isalways set to the binary value 1 to indicate the beginning of a validinstruction block. In other examples, different bit encodings can beused for the identification bit(s). In some examples, the instructionheader 320 includes information indicating a particular version of theISA for which the associated instruction block is encoded.

The instruction block header 320 also includes a store mask whichidentifies the load-store queue identifiers that are assigned to memorystore (and in some examples, memory load) operations. The instructionblock header can also include a write mask, which identifies whichglobal register(s) the associated instruction block will write. Theassociated register file must receive a write to each entry before theinstruction block can complete. In some examples a block-based processorarchitecture can include not only scalar instructions, but alsosingle-instruction multiple-data (SIMD) instructions, that allow foroperations with a larger number of data operands within a singleinstruction.

VI. Example Block-Based ISA Target Encoding

FIG. 4 is a diagram 400 depicting an example of two portions 410 and 415of C language source code and their respective instruction blocks 420and 425 (in assembly language), illustrating how block-basedinstructions can explicitly encode their targets. The high-level Clanguage source code can be translated to the low-level assemblylanguage and machine code by a compiler whose target is a block-basedprocessor. A high-level language can abstract out many of the details ofthe underlying computer architecture so that a programmer can focus onfunctionality of the program. In contrast, the machine code encodes theprogram according to the target computer's ISA so that it can beexecuted on the target computer, using the computer's hardwareresources. Assembly language is a human-readable form of machine code.

In the following examples, the assembly language instructions use thefollowing nomenclature: “|[number>]” specifies the number of theinstruction within the instruction block where the numbering begins atzero for the instruction following the instruction header and theinstruction number is incremented for each successive instruction; theoperation of the instruction (such as READ, ADDI, DIV, and the like)follows the instruction number; optional values (such as the immediatevalue 1) or references to registers (such as R0 for register 0) followthe operation; and optional targets that are to receive the results ofthe instruction follow the values and/or operation. Each of the targetscan be to another instruction, a broadcast channel to otherinstructions, or a register that can be visible to another instructionblock when the instruction block is committed. An example of aninstruction target is T[1R] which targets the right operand ofinstruction 1. An example of a register target is W[R0], where thetarget is written to register 0.

In the diagram 400, the first two READ instructions 430 and 431 of theinstruction block 420 target the right (T[2R]) and left (T[2L])operands, respectively, of the ADD instruction 432. In the illustratedISA, the read instruction is the only instruction that reads from theglobal register file; however any instruction can target, the globalregister file. When the ADD instruction 432 receives the result of bothregister reads it will become ready and execute.

When the TLEI (test-less-than-equal-immediate) instruction 433 receivesits single input operand from the ADD, it will become ready and execute.The test then produces a predicate operand that is broadcast on channelone (B[1P]) to all instructions listening on the broadcast channel,which in this example are the two predicated branch instructions (BRO_T434 and BRO_F 435). The branch that receives a matching predicate willfire.

A dependence graph 440 for the instruction block 420 is alsoillustrated, as an array 450 of instruction nodes and theircorresponding operand targets 455 and 456. This illustrates thecorrespondence between the instruction block 420, the correspondinginstruction window entries, and the underlying dataflow graphrepresented by the instructions. Here decoded instructions READ 430 andREAD 431 are ready to issue, as they have no input dependencies. As theyissue and execute, the values read from registers R6 and R7 are writteninto the right and left operand buffers of ADD 432, marking the left andright operands of ADD 432 “ready.” As a result, the ADD 432 instructionbecomes ready, issues to an ALU, executes, and the sum is written to theleft operand of TLEI 433.

In some examples, a larger instruction block may be processed in smallerportions to allow for allocation of processor resources to execute theblock. For example, a processor adapted to execute up to 128-wordinstruction blocks can be configured to process to the blocks in 32-wordportions. However, instruction results may need to be passed betweeninstruction block portions in certain examples. For example, the subi #1instruction 460 targets both the right operand of instruction number 4(“T[4R]”) and the right operand of instruction number 100 (“T[100R]”).Thus, when a processor is configured to process the instruction block insmaller portions, a results buffer is used to temporarily store thetarget operands of the instruction until the target instruction 465 canconsume its input operand(s).

As a comparison, a conventional out-of-order RISC or CISC processorwould dynamically build the dependence graph at runtime, usingadditional hardware complexity, power, area, and reducing clockfrequency and performance. However, the dependence graph is knownstatically at compile time and an EDGE compiler can directly encode theproducer-consumer relations between the instructions through the ISA,freeing the microarchitecture from rediscovering them dynamically. Thiscan potentially enable a simpler microarchitecture, reducing area, powerand boosting frequency and performance.

VII. Example Block-Based Instruction Formats

FIG. 5 is a diagram illustrating generalized examples of instructionformats for an instruction header 510, a generic instruction 520, abranch instruction 530, and a memory access instruction 540 (e.g., amemory load or store instruction). The instruction formats can be usedfor instruction blocks executed according to a number of execution flagsspecified in an instruction header that specify a mode of operation.Each of the instruction headers or instructions is labeled according tothe number of bits. For example the instruction header 510 includes four32-bit words and is labeled from its least significant bit (lsb) (bit 0)up to its most significant bit (msb) (bit 127). As shown, theinstruction header includes a write mask field, a number of exit typefields 511, a number of execution flag fields, an instruction block sizefield 512, and an instruction header ID bit (the least significant bitof the instruction header). In some examples, the instruction header 510includes additional metadata 515, which can be used to controladditional aspects of instruction block execution and performance. Thisincludes cache organization, execution lane organization,leader/follower instruction windows, or other forms of control to assistwith implementing wide memory load execution with wide cache lines.

The execution flag fields depicted in FIG. 5 occupy bits 6 through 13 ofthe instruction block header 510 and indicate one or more modes ofoperation for executing the instruction block. For example, the modes ofoperation can include core fission operation (e.g., by specifyingwhether the instruction block is to be executed using all or a portion,or with a quantity of execution resources), vector mode operation,branch predictor inhibition, memory dependence predictor inhibition,block synchronization, break after block, break before block, block fallthrough, and/or in-order or deterministic instruction execution. Theblock synchronization flag occupies bit 9 of the instruction block andinhibits speculative execution of the instruction block when set tologic 1.

The exit type fields include data that can be used to indicate the typesof control flow instructions encoded within the instruction block. Forexample, the exit type fields can indicate that the instruction blockincludes one or more of the following: sequential branch instructions,offset branch instructions, indirect branch instructions, callinstructions, and/or return instructions. In some examples, the branchinstructions can be any control flow instructions for transferringcontrol flow between instruction blocks, including relative and/orabsolute addresses, and using a conditional or unconditional predicate.The exit type fields can be used for branch prediction and speculativeexecution in addition to determining implicit control flow instructions.Addresses can be calculated for next instruction blocks to bespeculatively executed and stored in an instruction block addressregister. In some examples, up to six exit types can be encoded in theexit type fields, and the correspondence between fields andcorresponding explicit or implicit control flow instructions can bedetermined by, for example, examining control flow instructions in theinstruction block.

The illustrated generic block instruction 520 is stored as one 32-bitword and includes an opcode field, a predicate field, a broadcast IDfield (BID), a first target field (T1), and a second target field (T2).For instructions with more consumers than target fields, a compiler canbuild a fanout tree using move instructions, or it can assignhigh-fanout instructions to broadcasts. Broadcasts support sending anoperand over a lightweight network to any number of consumerinstructions in a core.

While the generic instruction format outlined by the generic instruction520 can represent some or all instructions processed by a block-basedprocessor, it will be readily understood by one of skill in the artthat, even for a particular example of an ISA, one or more of theinstruction fields may deviate from the generic format for particularinstructions. The opcode field specifies the operation(s) performed bythe instruction 520, such as memory read/write, register load/store,add, subtract, multiply, divide, shift, rotate, system operations, orother suitable instructions. The predicate field specifies the conditionunder which the instruction will execute. For example, the predicatefield can specify the value “true,” and the instruction will onlyexecute if a corresponding condition flag matches the specifiedpredicate value. In some examples, the predicate field specifies, atleast in part, which is used to compare the predicate, while in otherexamples, the execution is predicated on a flag set by a previousinstruction (e.g., the preceding instruction in the instruction block).In some examples, the predicate field can specify that the instructionwill always, or never, be executed. Thus, use of the predicate field canallow for denser object code, improved energy efficiency, and improvedprocessor performance, by reducing the number of branch instructions.

The target fields T1 and T2 specify the instructions to which theresults of the block-based instruction are sent. For example, an ADDinstruction at instruction slot 5 can specify that its computed resultwill be sent to instructions at slots 3 and 10, including specificationof the operand slot (e.g., left operation, right operand, or predicateoperand). Depending on the particular instruction and ISA, one or bothof the illustrated target fields can be replaced by other information,for example, the first target field T1 can be replaced by an immediateoperand, an additional opcode, specify two targets, etc.

The branch instruction 530 includes an opcode field, a predicate field,a broadcast ID field (BID), and an offset field. The opcode andpredicate fields are similar in format and function as describedregarding the generic instruction. The offset can be expressed in unitsof groups of four instructions, thus extending the memory address rangeover which a branch can be executed. The predicate shown with thegeneric instruction 520 and the branch instruction 530 can be used toavoid additional branching within an instruction block. For example,execution of a particular instruction can be predicated on the result ofa previous instruction (e.g., a comparison of two operands). If thepredicate is false, the instruction will not commit values calculated bythe particular instruction. If the predicate value does not match therequired predicate, the instruction does not issue. For example, a BRO_F(predicated false) instruction will issue if it is sent a falsepredicate value.

It should be readily understood that, as used herein, the term “branchinstruction” is not limited to changing program execution to a relativememory location, but also includes jumps to an absolute or symbolicmemory location, subroutine calls and returns, and other instructionsthat can modify the execution flow. The execution flow is modified bychanging the value of an instruction block address register (e.g., usinga branch instruction to implicitly change the value to point to thememory location of the next instruction block to execute), while inother examples, the execution flow can be changed by modifying a valuestored at a designated location in virtual memory (e.g., by a memorycontroller configured to detect reads and write to designated memorylocation and store/load the values to an instruction block addressregister). In some examples, a jump register branch instruction is usedto jump to a memory location stored in a register. In some examples,subroutine calls and returns are implemented using jump and link andjump register instructions, respectively.

The memory access instruction 540 format includes an opcode field, apredicate field, a broadcast ID field (BID), an immediate field (IMM)offset field, and a target field. The opcode, broadcast, predicatefields are similar in format and function as described regarding thegeneric instruction. For example, execution of a particular instructioncan be predicated on the result of a previous instruction (e.g., acomparison of two operands). If the predicate is false, the instructionwill not commit values calculated by the particular instruction. If thepredicate value does not match the required predicate, the instructiondoes not issue. The immediate field (e.g., and shifted a number of bits)can be used as an offset for the operand sent to the load or storeinstruction. The operand plus (shifted) immediate offset is used as amemory address for the load/store instruction (e.g., an address to readdata from, or store data to, in memory).

VIII. Example States of a Processor Core

FIG. 6 is a flowchart illustrating an example of a progression of states600 of a block-based processor core example of a computer implementedaccording to the disclosed technology. The computer includes multipleprocessor cores that are collectively used to run or execute a softwareprogram. The program can be written in a variety of high-level languagesand then compiled for the block-based processor using a compiler thattargets the block-based processor. The compiler can emit code that, whenrun or executed on the block-based processor, will perform thefunctionality specified by the high-level program. The compiled code canbe stored in a computer-readable memory that can be accessed by theblock-based processor. The compiled code can include a stream ofinstructions grouped into a series of instruction blocks. Duringexecution, one or more of the instruction blocks can be executed by theblock-based processor to perform the functionality of the program.Typically, the program will include more instruction blocks than can beexecuted on the cores at any one time. Thus, blocks of the program aremapped to respective cores, the cores perform the work specified by theblocks, and then the blocks on respective cores are replaced withdifferent blocks until the program is complete. Some of the instructionblocks may be executed more than once, such as during a loop or asubroutine of the program. An “instance” of an instruction block can becreated for each time the instruction block will be executed. Thus, eachrepetition of an instruction block can use a different instance of theinstruction block. As the program is run, the respective instructionblocks can be mapped to and executed on the processor cores based onarchitectural constraints, available hardware resources, and the dynamicflow of the program. During execution of the program, the respectiveprocessor cores can transition through a progression of states 600, sothat one core can be in one state and another core can be in a differentstate.

At state 605, a state of a respective processor core can be unmapped. Anunmapped processor core is a core that is not currently assigned toexecute an instance of an instruction block. For example, the processorcore can be unmapped before the program begins execution on theblock-based computer. As another example, the processor core can beunmapped after the program begins executing but not all of the cores arebeing used. In particular, the instruction blocks of the program areexecuted, at least in part, according to the dynamic flow of theprogram. Some parts of the program may flow generally serially orsequentially, such as when a later instruction block depends on resultsfrom an earlier instruction block. Other parts of the program may have amore parallel flow, such as when multiple instruction blocks can executeat the same time without using the results of the other blocks executingin parallel. Fewer cores can be used to execute the program during moresequential streams of the program and more cores can be used to executethe program during more parallel streams of the program.

At state 610, the state of the respective processor core can be mapped.A mapped processor core is a core that is currently assigned to executean instance of an instruction block. When the instruction block ismapped to a specific processor core, the instruction block is in-flight.An in-flight instruction block is a block that is targeted to aparticular core of the block-based processor, and the block will be oris executing, either speculatively or non-speculatively, on theparticular processor core. In particular, the in-flight instructionblocks correspond to the instruction blocks mapped to processor cores instates 610-650. A block executes non-speculatively when it is knownduring mapping of the block that the program will use the work providedby the executing instruction block. A block executes speculatively whenit is not known during mapping whether the program will or will not usethe work provided by the executing instruction block. Executing a blockspeculatively can potentially increase performance, such as when thespeculative block is started earlier than if the block were to bestarted after or when it is known that the work of the block will beused. However, executing speculatively can potentially increase theenergy used when executing the program, such as when the speculativework is not used by the program.

A block-based processor includes a finite number of homogeneous orheterogeneous processor cores. A typical program can include moreinstruction blocks than can fit onto the processor cores. Thus, therespective instruction blocks of a program will generally share theprocessor cores with the other instruction blocks of the program. Inother words, a given core may execute the instructions of severaldifferent instruction blocks during the execution of a program. Having afinite number of processor cores also means that execution of theprogram may stall or be delayed when all of the processor cores are busyexecuting instruction blocks and no new cores are available fordispatch. When a processor core becomes available, an instance of aninstruction block can be mapped to the processor core.

An instruction block scheduler can assign which instruction block willexecute on which processor core and when the instruction block will beexecuted. The mapping can be based on a variety of factors, such as atarget energy to be used for the execution, the number and configurationof the processor cores, the current and/or former usage of the processorcores, the dynamic flow of the program, whether speculative execution isenabled, a confidence level that a speculative block will be executed,and other factors. An instance of an instruction block can be mapped toa processor core that is currently available (such as when noinstruction block is currently executing on it). In one embodiment, theinstance of the instruction block can be mapped to a processor core thatis currently busy (such as when the core is executing a differentinstance of an instruction block) and the later-mapped instance canbegin when the earlier-mapped instance is complete.

At state 620, the state of the respective processor core can be fetch.For example, the IF pipeline stage of the processor core can be activeduring the fetch state. Fetching an instruction block can includetransferring the block from memory (such as the L1 cache, the L2 cache,or main memory) to the processor core, and reading instructions fromlocal buffers of the processor core so that the instructions can bedecoded. For example, the instructions of the instruction block can beloaded into an instruction cache, buffer, or registers of the processorcore. Multiple instructions of the instruction block can be fetched inparallel (e.g., at the same time) during the same clock cycle. The fetchstate can be multiple cycles long and can overlap with the decode (630)and execute (640) states when the processor core is pipelined.

When instructions of the instruction block are loaded onto the processorcore, the instruction block is resident on the processor core. Theinstruction block is partially resident when some, but not all,instructions of the instruction block are loaded. The instruction blockis fully resident when all instructions of the instruction block areloaded. The instruction block will be resident on the processor coreuntil the processor core is reset or a different instruction block isfetched onto the processor core. In particular, an instruction block isresident in the processor core when the core is in states 620-670.

At state 630, the state of the respective processor core can be decode.For example, the DC pipeline stage of the processor core can be activeduring the fetch state. During the decode state, instructions of theinstruction block are being decoded so that they can be stored in thememory store of the instruction window of the processor core. Inparticular, the instructions can be transformed from relatively compactmachine code, to a less compact representation that can be used tocontrol hardware resources of the processor core. The decode state canbe multiple cycles long and can overlap with the fetch (620) and execute(640) states when the processor core is pipelined. After an instructionof the instruction block is decoded, it can be executed when alldependencies of the instruction are met.

At state 640, the state of the respective processor core can be execute.The execute state can include various modes of operation, such as adefault execution mode and a debug mode. During the default mode of theexecute state, instructions of the instruction block are being executed.In particular, the EX and/or LS pipeline stages of the processor corecan be active during the execute state. The instruction block can beexecuting speculatively or non-speculatively. A speculative block canexecute to completion or it can be terminated prior to completion, suchas when it is determined that work performed by the speculative blockwill not be used. When an instruction block is terminated, the processorcan transition to the abort state. A speculative block can complete whenit is determined the work of the block will be used, all register writesare buffered, all writes to memory are buffered, and a branch target iscalculated, for example. A non-speculative block can execute tocompletion when all register writes are buffered, all writes to memoryare buffered, and a branch target is calculated, for example. Theexecute state can be multiple cycles long and can overlap with the fetch(620) and decode (630) states when the processor core is pipelined. Whenthe instruction block is complete, the processor can transition to thecommit state.

During the debug mode of the execute state, instructions of theinstruction block can be single-stepped or executed one at a time. Forexample, the processor core can be halted in the debug mode of theexecute state, such as when a control signal is asserted or when theinstruction header specifies that the debug mode is to be used for theinstruction block. Upon receiving an indication to perform a single-stepoperation, one instruction of the instruction block can be executed. Theintermediate state of the processor core can be scanned or read out ofthe processor core. The process can be repeated for the next instructionof the instruction block upon receiving another indication to perform asingle-step operation. The “next” instruction can be determined based ona compiler-generated order, a scheduler-generated order, or an ordergenerated outside of the processor core (such as by debug softwarerunning on a different core). The instructions of the block can continueto be single-stepped until the commit conditions are met, and then theprocessor can transition to the commit state.

At state 650, the state of the respective processor core can be set tocommit or abort. During commit, the work of the instructions of theinstruction block can be atomically committed so that other blocks canuse the work of the instructions. In particular, the commit state caninclude a commit phase where locally buffered architectural state iswritten to architectural state that is visible to or accessible by otherprocessor cores. When the visible architectural state is updated, acommit signal can be issued and the processor core can be released sothat another instruction block can be executed on the processor core.During the abort state, the pipeline of the core can be halted to reducedynamic power dissipation. In some applications, the core can be powergated to reduce static power dissipation. At the conclusion of thecommit/abort states, the processor core can receive a new instructionblock to be executed on the processor core, the core can be refreshed,the core can be idled, or the core can be reset.

In certain examples of the disclosed technology, an instruction block isdivided into portions and the individual portions are executed usingdifferent spatially and/or temporally allocated resources. For example,an execution slice of a processor may be adapted to handle 32-wordportions of an instruction block. When all the instructions of a portionhave executed, then the results produced by this respective portion maybe partially committed. In some examples, the partially committedresults are actually written to an architectural register file,temporarily stored in a physical register file, and/or actually writtento memory. In other examples, the partially committed results aretemporarily stored until it is determined whether the entire instructionblock will be committed or aborted.

At state 660, it can be determined if the instruction block hasadditional portions to fetch, decode and execute. For example, if theinstruction block size is greater than the maximum number ofinstructions that can be processed by the current context's allocatedresources, results from the current portion are stored in a resultsbuffer, and the processor proceeds to state 620 in order to fetch,decode, and execute instructions for a subsequent portion of theinstruction block. In some examples, the portions may be concurrentlyfetched, decoded, and executed by allocating multiple slices ofexecution logic to the context. If the instruction block size is equalor less than the maximum number of instructions that can be processed bythe current context's allocated resources, or if there are no remainingportion of the current instruction block to execute, the processorproceeds to state 670.

At state 670, the state of the respective processor core can be idle.The performance and power consumption of the block-based processor canpotentially be adjusted or traded off based on the number of processorcores that are active at a given time. For example, performingspeculative work on concurrently running cores may increase the speed ofa computation but increase the power if the speculative mispredictionrate is high. As another example, immediately allocating new instructionblocks to processors after committing or aborting an earlier executedinstruction block may increase the number of processors executingconcurrently, but may reduce the opportunity to reuse instruction blocksthat were resident on the processor cores. Reuse may be increased when acache or pool of idle processor cores is maintained. For example, when aprocessor core commits a commonly used instruction block, the processorcore can be placed in the idle pool so that the core can be refreshedthe next time that the same instruction block is to be executed. Asdescribed above, refreshing the processor core can save the time andenergy used to fetch and decode the resident instruction block. Theinstruction blocks/processor cores to place in an idle cache can bedetermined based on a static analysis performed by the compiler or adynamic analysis performed by the instruction block scheduler. Forexample, a compiler hint indicating potential reuse of the instructionblock can be placed in the header of the block and the instruction blockscheduler can use the hint to determine if the block will be idled orreallocated to a different instruction block after committing theinstruction block. When idling, the processor core can be placed in alow-power state to reduce dynamic power consumption, for example.

At state 680, it can be determined if the instruction block resident onthe idle processor core can be refreshed. If the core is to berefreshed, the block refresh signal can be asserted and the core cantransition to the execute state (640). If the core is not going to berefreshed, the block reset signal can be asserted and the core cantransition to the unmapped state (605). When the core is reset, the corecan be put into a pool with other unmapped cores so that the instructionblock scheduler can allocate a new instruction block to the core.

IX. Example Processor Microarchitecture with Sharding Circuit

FIG. 7 is a block diagram 700 outlining an example microarchitecture fora processor datapath in which certain aspects of the disclosedtechnology can be implemented. For example, processors implementinggeneral purpose RISC ISAs, CISC ISAs, block-based processor ISAs,including EDGE ISAs, or other ISAs can be implemented usingarchitectures similar to that illustrated in the block diagram 700. Themicroarchitecture depicted can be implemented in any suitabletechnology, including as an integrated circuit, an SOC, or withprogrammable logic, such as in an FPGA. The example microprocessormicroarchitecture can include one or more register files (e.g., such asthe register file 290 discussed above) and other components, which arenot depicted to simplify explanation of other depicted features.

As shown in FIG. 7, the example datapath includes a set of operandbuffers 710, which store operand data to be processed by a number ofexecution units 720. The execution units 720 output the results of theiroperations to a number of pipeline registers 725. Data from the pipelineregisters 725 is output to a write port 270-1 of the load/store queue270 and to a writeback circuit 730. In contrast to “writeback”operations in traditional CISC processors, which send data to theregister file, the disclosed writeback circuit 730 can send data fromthe execution units 720 (e.g., via the pipeline registers 725) to theoperand buffers 710 or in some cases, bypass the operand buffers andsend data to the execution units.

The data path of the example microarchitecture is divided into a numberof segments or “execution lanes,” as indicated by the dashed lines. Inthe illustrated example, there are sixteen execution lanes, each of thelanes processing a 16-bit word (e.g., bits 255:252 or 15:0). The operandbuffers 710 store operands for each of the sixteen segments. Each of theexecution units 720 can include in one or more suitable execution units,including but not limited to: adders, multipliers, arithmetic and logicunits (ALUs), shifters, rotators, floating point units, or other suchsuitable execution units. The control unit for the processor generatescontrol signals that are used to configure operation of the executionunits 720.

The microarchitecture further includes the data cache 275, which in thisexample is arranged in a number of banks, 275-1 . . . 275-N. The datacache 275 can output a plurality of N words at a time, one word fromeach bank of the data cache. As used herein, a collection of two or morewords output from the data cache 275 at a single time is dubbed a “cacheline.” The cache line of data is output by a wide memory load circuitthat concurrently loads to or more words from a cache line of the datacache 275. By having a wide cache line, a large amount of data can beread from memory in a particular clock cycle of the processor. In someexamples, the words forming the data output by the cache line arearranged adjacently in memory. In the example of FIG. 7, the cache lineincludes 16 words, each of the words having 16 bits. In other examples,different numbers of words and different size words may be employed. Inother examples, other arrangements of the words may be provided withfurther configuration of a memory management unit (MMU) that controlsoperation of the data cache. An entire cache line worth of data can beoutput directly to the writeback circuit 730. Data from the cache linecan alternatively be output to a read port 270-2 of the load/store queue(LSQ).

As shown FIG. 7, the writeback circuit 730 can receive data from threesources: results operands received from the output of the pipelineregisters 725, data for an entire cache line of data from the data cache275, or data from the read port 270-2 of the load/store queue. Thewriteback circuit 730 can output data to a sharding circuit 750, whichrearranges input data prior to sending to the operand buffers 710. Theillustrated writeback circuit 730 can also bypass the operand buffers710 and send data directly to the execution unit 720. Thus, thewriteback circuit 730 can send data to be stored in the operand buffers710. In some examples, data that is not going to be used by otherinstructions of an instruction block or otherwise does not need to bestored can be sent directly to the execution units 720 via bypass path.The writeback circuit 730 can be implemented using any suitableinterconnect and logic technology. For example, interconnect wires canbring data to selection logic, such as a logic multiplexer, pass-gatemultiplexer, transmission gate multiplexer, tri-state bus, or othersuitable selection logic. For photonic circuit implementations of thedisclosed technology, logically equivalent selection logic andinterconnect routing can be used.

In the illustrated example, the writeback circuit 730 sends data from aselected one of the three depicted sources to a sharding circuit 750that is coupled to the input of the operand buffers 710. In otherexamples, there is no sharding circuit. In other examples, the shardingcircuit may be situated between the operand buffers 710 and theexecution units 720, or be situated between the output of the executionpipeline registers 725 and the load store queue 270 or writeback circuit730. In other examples, a sharding circuit can be situated at the outputof the cache line 740 and send data on to the writeback circuit 730.

The sharding circuit 750 can perform various manipulations of dataoperands received. In the illustration of FIG. 7, the sharding circuit750 is performing bitwise interleaving of bits within each individualreceived word. In other examples, the sharding circuit 750 can rearrangereceived words, for example by shifting individual words one or morewords over, by rotating words, by transposing bits within the words,swapping words, extracting words, and/or extending words. In someexamples, the sharding circuit 750 is coupled to the wide memory loadcircuit cache line 740 and is configured to select individual words fromthe cache line 740 and send each of the selected words to a selectedwriteback channel of the writeback circuit 730 or to selected executionlanes of the operand buffers 710. In some examples, each input word tothe sharding circuit 750 his output to the respective output word lane.In other examples, one or more but not all of the input words areselected and output. In some examples, the sharding circuit can beconfigured to mask one or more output words (e.g., with a predeterminedpattern of all ones, all zeroes, or other predetermined pattern of onesand zeroes).

Also shown in FIG. 7, the execution units 720 can be configured tooperate in a scaler mode, where data for each of the execution lanes isprocessed as a complete set of bits, for example as shown on the rightexecution unit 720-N, where the ALU is configured to operate on anentire 16-bit word of data, or for smaller numbers of bits in SIMDoperation, where the left ALU of the execution unit 720-1 is configuredto perform operations on four individual 4-bit chunks of data using areconfigured 16-bit ALU.

The example microarchitecture of FIG. 7 can further include additionalselection and/or multiplexing logic. For example, the operand buffers710 may be configured to receive data from other sources besides thesharding circuit 750. For example, immediate values or register valuescan be received at the inputs to the operand buffer 710. In someexamples, the sharding circuit 750 can be configured to pass throughnon-rearranged data, without bit-wise or word-wise manipulations of theinput data.

A processor datapath configured according to the microarchitecture ofFIG. 7 can be configured to perform a method comprising concurrentlyloading a plurality of two or more words from a single word of the datacache line 740 and sending a selected word of the plurality of words toa selected one of the execution lanes of the processor. For example, thesharding circuit 750 can select one word from the received cache line740 and send it to a selected execution lane of the operand buffers 710.

In some examples, the microarchitecture further includes separate levelone (L1) instruction cache and L1 data cache 275. In some examples orconfigurations, the instruction cache and the data cache 275 can beshared across all active contexts. In other examples, one or both of theinstruction cache and data cache 275 are partitioned into a number N ofseparate banks (e.g., 275-1, 275-2, . . . , 275-N). In examples,additional control logic is used to maintain cache coherency.

Each of the execution units 720 (e.g., 720-1 or 720-N) contain executionlogic used for performing operations associated with instructions, forexample, instructions in an EDGE instruction block. The examplemicroarchitecture processor can be configured such that the executionlanes are allocated to one, two, three, or four different contexts. Forexample, all of the execution units 720 can be allocated for executionof a single context by the processor. The processor can later bereconfigured such that a first execution unit 720-1 is used to execute afirst context, a second execution unit is used to execute a secondcontext, and so forth. In other examples, vector operation can beimplemented by configuring one of the execution lanes to be a “leader”lane, and configuring the other execution lanes to follow operation ofthe leader lane.

Each of the execution lanes can be configured to include similarexecution resources, including, by example, an instruction windowsegment, a first portion of the operand buffer 710, and second portionof the operand buffer 710, and one or more execution units, including,for example, execution units 720-1 or 720-N. The illustrated executionunits can include, for example, integer arithmetic and logic units(ALU), adders, subtractors, multipliers, dividers, shifters, rotators,or other suitable execution units. In some examples, a floating pointunit (FPU) is included and can be shared by any of the contextsexecuting with any of the illustrated functional slices 761-764. Inother examples, FPUs and other specialized logic, such as DSPs orgraphics functions can be shared, or can be included within an executionlane and thus not shared outside of the context currently assigned tothe slice or slices.

The instruction window segment for at least the leader execution lanestores information such as decoded instructions, state information forthe current execution state of the instruction block, as well as controllogic for controlling execution of the context upon the instructionslice or slices. In some examples, an execution lane can execute morethan one instruction per clock cycle (e.g., by using plural arithmeticor logic units within an execution lane). The instruction window segmentcan further include logic for providing control speculation. The operandbuffers temporarily store operands generated for and consumed byinstructions within an instruction block mapped to the functional slice.For example, in an EDGE ISA, data operands generated by an instructioncan be temporarily stored in one of the operand buffers before beingused by one of the functional units, and the result sent to theinstructions target.

X. Example Microarchitecture Configured for Word Sharding Operation

FIG. 8 is a block diagram 800 depicting an example micro architecturedata path that has been configured to perform word-wise sharding, as canbe performed in certain examples of the disclosed technology. The datapath includes a sharding circuit 810, operand buffers 820, executionunits 830, and a wide memory load circuit coupled to a writeback path840. The sharding circuit 810, the operand buffers 820, and theexecution units 830 are arranged into a plurality of execution lanes850-1 through 850-N. As shown, data read from the writeback circuit 840has input as a number of individual words 860, 861, 862, 863, etc. Thesharding circuit outputs each of the words at a relative position thatis one word to the left. For example, input word 863 is output as a word873, one execution lane over. The leftmost input word 860 is wrapped tobe output at the right most output word 870. Thus, the sharding circuit810 performs word-wise sharding, unlike the configuration shown in FIG.7, where the sharding circuit 750 manipulates bits within a word on asingle or multiple bit basis.

XI. Example Microarchitecture Configured for Bypass Operation

FIG. 9 as a block diagram 900 of an example micro architecture for aprocessor data path, as can be implemented in certain examples of thedisclosed technology. As shown in FIG. 9, a first wide cache line ofdata A has been read from a wide data cache line and provided as inputto a sharding circuit 910. The sharding circuit 910 can perform variousmanipulations as discussed above, including bitwise and word-wisemanipulations. The output of the sharding circuit 910 is stored in anumber of operand buffers. On a subsequent clock cycle, a second widecache line of data B is output and sent by the writeback circuit 940along a bypass path directly to the execution units 930. For example,the data B can be sent in the very next clock cycles after the firstwide cache line A is loaded. In other examples, one or more clock cyclesintervenes between the read of A and B by the writeback circuit 940.Control logic is used to configure the execution unit selection logic toselect a word (e.g., A₀, A₁, or A₇) of operand data to combine with aword of the operand data B (e.g., B₁, B₂, or B₀, respectively) forperforming an arithmetic or logical operation. Each of the words ofoperand data A (e.g., A₀, A₁, or A₇) has been shifted one position tothe left by the sharding circuit 910. The second wide word of cache linedata B is not shifted in this example. For example, the products A₀ B₁,A₁ B₂, and/or A₇ B₀, are generated when the execution units 930 areconfigured to perform multiplication for the respective input of anexecution lane. Thus, complex operations can be performed relativelyquickly through the use of the sharding circuit 910 and bypass pathprovided by the writeback circuit 940.

As shown in FIG. 9, the sharding circuit 910, the operand buffers 920,the execution units 930, and the instruction windows 950 are allconfigured as separate segments or execution lanes. In the illustratedexample, a first instruction window 950-1 is designated as the “leader”instruction window. Control signals generated by the leader instructionwindow 950-1 can be used to control operation of the follower'sinstruction windows, for example instruction windows 950-5, 950-6,and/or 950-7. In other examples, one or more of the instruction windowscan operate independently of the leader instruction window 950-1.

XII. Example Microarchitecture with Fewer Execution Units Per Segment

FIG. 10 is a block diagram 1000 outlining an example micro architecturedatapath for performing wide load memory operations, as can be performedin certain examples of the disclosed technology. Similar to the microarchitecture discussed above regarding FIG. 9, a leader instructionwindow 1050-1, a sharding circuit 1010, and operand buffers 1020 areconfigured into eight execution lanes. But, in this example, the datapath includes half the number of execution units 1030. Additionalmultiplexer logic 1035 has been added in order to select either a highportion of words from the operand buffer 1020 or a low portion of wordsfrom the operand buffer. Thus, operations requiring data for all eightexecution lanes can be performed across two clock cycles by processingone half of the execution lanes using the execution units 1030 during afirst clock cycle and then processing operations for a second half ofthe execution lanes using the execution units in a second clock cycle.In this manner, integrated circuit real estate can be conserved byreducing the amount active device area and interconnect resourcesdedicated to the execution units 1030.

XIII. Example Microarchitecture with Fewer Execution Units

FIGS. 11A-11 C outline an example portion of an execution lane whileperforming a multiply-reduce operation, as can be performed in certainexamples of the disclosed technology. For example, the reconfiguredexecution units 720 discussed above can be reconfigured to perform thedepicted operations. As shown in FIG. 11A, a 32-bit wide execution unit1110 is configured into four individual 8-bit SIMD units. A shardingcircuit has been used to arrange data received from the data cache intointerlaced, zero-padded packets of 4-bits as shown. For example, a firstwide 16-bit wide data cache line input A is unpacked into 4-bitportions: a₀, a₁, a₂, and a₃. A second, 16-bit wide data cache lineinput B is also arranged into 4-bit portions b₀, b₁, b₂, and b₃. Thesevalues are output from an operand buffer (and/or bypass path of awriteback circuit) into the execution unit 1110, which performs parallelSIMD operations to generate four 8-bit products a₀b₀, a₁b₁, a₂b₂, anda₃b₃ stored in an output register 1120.

FIG. 11B shows the state of the datapath after the values in the outputregister 1120 have been copied to two operand buffer registers 1130 and1135. The execution unit 1110 is reconfigured 1111 to add the two 8-bitwide terms, producing two 16-bit wide outputs. Thus, the partiallyreduced products are temporarily stored in the output register 1120.

FIG. 11C depicts the data path after the intermediate product 1130 hasbeen copied into two operand buffers 1140 and 1145. These operandbuffers are combined in a single 16-bit operation producing a completed32-bit output 1150 which is the reduction of all of the productsproduced at the first step shown in FIG. 11A.

XIV. Example Alternative Arrangements of Sharding Circuit

FIG. 12 is a block diagram 1200 outlining an example datapath for amicroarchitecture in which certain examples of the disclosed technologycan be implemented. As shown in FIG. 12, a sharding unit 1210 has beenconfigured so that it is situated between execution unit outputregisters 1235 and the write port 1240 of a datapath. As shown, thesharding circuit 1210 is configured for a word swap operation, whereinthe leftmost word leftmost input word is output as the right most outputword, and the right most input word is output aft as the leftmost outputword. Intermediate input words are correspondingly swapped as shown.Thus, in the illustrated example, sharding operations can be performedat different positions within the datapath, for example, the shardingcan be applied before the data is output to the LSQ write port 1240.

XV. Example Method of Concurrent Cache Loading

FIG. 13 is a flow chart 1300 outlining an example method of loadingmultiple words from data cache, as can be performed in certain examplesof the disclosed technology. For example, a general purpose orblock-based processor including a data path such as those discussedabove regarding FIGS. 7 through 12 can be used to implement theillustrated method.

Process block 1310, two or more words are loaded concurrently from asingle report of a data cache. The complete collection of the pluralityof words can also be referred to as a cache line. In some examples, eachof the words of the cache line includes bytes that are adjacentlylocated in memory. In other examples, the bytes may be spaced at regularintervals or arrange a memory in a different manner. The loading can beperformed using a wide memory load circuit.

At process block 1320, at least one word of the concurrently loadedwords is selected and sent to a respective selected lane of one of theprocessors execution lanes. For example, the words can be sent to theexecution lanes in the same order in which they have been loaded fromthe data cache. In other examples, the ordering of the words can bereversed, swizzled, replicated, or otherwise rearranged. In someexamples, a sharding circuit is used to rearrange the words. In someexamples, a selected individual word of the plurality words is sent to arespective selective one of the execution lanes of a processor. In someexamples, the selected word is sent to an operand buffer. In someexamples, the selected word bypasses the processor operand buffer and issent directly to execution resources of the selected execution lane.

At process block 1330, operations are performed for the selected wordfor each of the respective processor execution lanes. In some examples,performing operations includes performing SIMD operations for two ormore separate portions of the selected word. In some examples, thereceived word is received via a writeback path circuit and the receivedword is multiplied by an output word of the operand, thereby producing aproduct. In some examples, performing operations further includesconcurrently loading a second cache line of two or more words from areport of a data cache and adding a second selected word of the secondcache line to a product.

In some examples, the method includes using a sharding circuit toreorder and send the respective word from the writeback path to adifferent one of selected execution lanes. Some examples, the shardingcircuit reorders respective words by performing at least one of thefollowing operations: shift, rotate, reverse, move, swap, transpose,extract, or extend. In some examples, a SIMD operation is performedseparately for each of two or more portions of the respective word. Insome examples, a compiler is used to identify at least one vectoroperation in code for at least one instruction block and to emit objectcode for the at least one instruction block that, when the object codeis executed by a processor, causes the processor to perform theillustrated method.

XVI. Example Method of Concurrent Cache Loading

FIG. 14 is a flow chart 1400 outlining an example method of concurrentlyloading words from a wide data cache line and sending the loaded wordsto an operand buffer or bypassing the operand buffer, as can beperformed in certain examples of the disclosed technology.

At process block 1410, two words are concurrently loaded from a singleoutput of a data cache line. For example, wide memory load circuits suchas those discussed above can be used to implement the cache line read.Processor control logic makes a determination whether or not to send theloaded words to the date a path operand buffer or to bypass the operandbuffer and send the selected words directly to an execution lane. Insome examples, the determination is based on control bits encoded in aprocessor instruction. In other examples, control logic is used toanalyze dependencies between plural instructions and determine whetherbypass operation can be safely performed. If it is determined that thewords are to be sent to the operand buffer, the method proceeds toprocess block 1420. Conversely, if it is determined that the operandbuffer is to be bypassed, the method proceeds to process block 1430.

At process block 1420, the selected word(s) are sent to an operandbuffer of its respective execution lane. For example, a writeback pathsituated at the output of a wide memory load circuit can be used to sendthe words to the appropriate input of the operand buffer. The data canbe stored in the operand buffer until a consuming instruction is readyto issue, and then the data can be sent to the appropriate executionunits in the processor data path.

At process block 1430, the selected word bypasses the processor operandbuffers and is sent directly to the selected execution lane of theprocessor data path. In some examples, the bypassed data is combinedwith other data output by the operand buffer and combined in operationsperformed by the execution units. For example, previously multipliedoperands stored in the operand buffer can be combined with data readfrom the data cache that has bypassed the operand buffer producing aresult of the output of the execution units.

In some examples, words of the cache line or of the execution lanes canbe reordered or rearranged using a sharding circuit. For example, asharding circuit can be used to perform word-wise or bitwise reorderingof data after it is loaded from the cache line at process block 1410. Insome examples, a sharding circuit is located along the bypassed path, orat the output of the execution units and reordering operations performedbefore storing the output data in the data cache memory. The shardingcircuit can be configured according to control bits encoded withinindividual instructions, in an instruction block instruction header, orby determining dependencies or optimization's between instructions. Insome examples, a compiler is used to identify at least one vectoroperation in code for at least one instruction block and to emit objectcode for the at least one instruction block that, when the object codeis executed by a processor, causes the processor to perform theillustrated method.

XVII. Example Method of Concurrent Cache Loading

FIG. 15 is a flow chart 1500 outlining an example method of schedulingoperations specified by an instruction block as can be performed incertain examples of the disclosed technology. For example, any of thedatapaths discussed above can be used to implement the illustratedmethod.

At process block 1510, object code is received for an instruction block.For example, pre-compiled instructions can be stored in memory or astorage device and retrieved and sent to the processor control logic. Inother examples, an interpreter or just-in-time compiler is used to emitthe received object code.

At process block 1520, operations are scheduled that have been specifiedby an instruction block for two or more instruction lanes. For example,based on the arrangement of instructions in memory, instructionidentifiers, dependencies between instructions, LSID, or other methodsof specifying operations are scheduled. For example, to calculate aninner product, multiply operations are scheduled to perform before addoperations. If the number of execution units is less than the number ofinstruction windows, operations performed may be scheduled back to backon, for example half of the branch to be performed.

At process block 1530, memory operations are performed for at least oneword read from the cache line. Each of the plural words of the cacheline is associated with one of the execution lanes.

In some examples, the memory operation is a load operation andperforming the memory operation includes sending each of respectiveplural words to a different execution lane of the processor. Someexamples, the memory operation as a store operation and the performingthe memory operation includes sending each of the respective pluralwords from its associated execution lane to a selected word of the samecache line of the data cache for writing to memory coupled to theprocessor. In some examples, performing the memory operation includesperforming a sharding operation for the plural words after loading thewords or before storing the words in the data cache. In some examples, acompiler is used to identify at least one vector operation in code forat least one instruction block and to emit object code for the at leastone instruction block that, when the object code is executed by aprocessor, causes the processor to perform the illustrated method.

XVIII. Example Code and Scheduling for a Matrix-Vector MultiplicationLoop

FIGS. 16A and 16B are source code 1600 and assembly code 1620 forperforming a matrix-vector multiplication entered looped with ablock-based processor, as can be implemented using data paths havingdisclosed memory load circuits and writeback paths, according to certainexamples of the disclosed technology. As shown, an inner loop includesmultiplying elements of a first matrix A with elements of a secondmatrix B. The products resulting from the multiplication are reduced byadding to the vector C. The associated assembly code 1620 forimplementing the multiplication inner loop includes a multiply (MUL) andan addition (ADD) instruction. If these multiply and add instructionsare mapped to plural execution lanes, a bottleneck may form because ofthe number of memory load operations (LD) the need to be performed.Thus, these operations may be sped up by allowing for a wide memory loadcircuit to concurrently load to or more operand words from a cache lineof the associated data cache.

FIGS. 17A-B are source code 1700 and assembly code 1720 for performing amatrix-vector multiplication similar to that illustrated above regardingFIGS. 16A and 16B. However, the source code has been re-factored asillustrated such that the reduced operation is performed for every eightsets of elements of the matrix factors. This re-factoring allows forcalculation of intermediate reduced values while performing the matrixmultiply. This can be mapped onto data paths according to this disclosedtechnology, thereby increasing throughput of the processor.

FIG. 17C is source code 1740 for performing a matrix-vectormultiplication similar to that illustrated above regarding FIGS. 16A and16B. However, the multiple and reduce instructions have been replacedwith SIMD instructions using 16-bit wide packed operands, as indicated1760. Use of the packed operands can allow for more operations to occurper clock cycle, trading off number of bits of precision for additionalparallel operations.

FIG. 18A is a table 1800 illustrating an example schedule of a matrixmultiply on a processor having four execution lanes. The exampleprocessor can only read one word from the data cache at a time, thus,the load instructions must be staggered across different clock cyclesfor the four execution lanes. Thus, as shown, the load, multiply,reduce, and store operations are staggered in time for the four blocks,as indicated by the dashed lines 1810. For example, instruction lane 1performs its memory load instructions during clock cycles numbers 10 and11. The memory load operations for execution lane number 4 is notperformed until clock cycles numbers 16 and 17. Thus, total throughputof the processor is not optimal, as the execution units of eachexecution lane are stalled while the other memory load operations areperformed for other execution lanes. Thus, throughput could be improvedby allowing for reading of wide data cache lines concurrently.

FIG. 18B is a table 1820 illustrating an example scheduling of a matrixmultiply onto a processor having for execution lanes. The exampleprocessor is configured so that it can read at least 16 words from adata cache at one time. Thus, as shown, the memory load operations forall four execution lanes is performed during clock cycles 8 and 9, asindicated by the dashed lines 1830. Thus, the associated multiplyinstructions can occur at clock cycle 10, and the reduced operations canoccur for all execution lanes at clock cycle 11. Thus, the total numberof clock cycles required to complete the illustrated task is reducedfrom 20 clock cycles to 12 clock cycles.

XIX. Example Computing Environment

FIG. 19 illustrates a generalized example of a suitable computingenvironment 1900 in which described embodiments, techniques, andtechnologies, including sharding and writeback operations performed forwide, multi-word cache lines coupled to a general purpose or block-basedprocessor, can be implemented.

The computing environment 1900 is not intended to suggest any limitationas to scope of use or functionality of the technology, as the technologymay be implemented in diverse general-purpose or special-purposecomputing environments. For example, the disclosed technology may beimplemented with other computer system configurations, including handheld devices, multi-processor systems, programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike. The disclosed technology may also be practiced in distributedcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed computing environment, program modules (including executableinstructions for block-based instruction blocks) may be located in bothlocal and remote memory storage devices.

With reference to FIG. 19, the computing environment 1900 includes atleast one processing unit 1910 and memory 1920. In FIG. 19, this mostbasic configuration 1930 is included within a dashed line. Theprocessing unit 1910 executes computer-executable instructions and maybe a real or a virtual processor. In a multi-processing system, multipleprocessing units execute computer-executable instructions to increaseprocessing power and as such, multiple processors can be runningsimultaneously. The memory 1920 may be volatile memory (e.g., registers,cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory,etc.), or some combination of the two. The memory 1920 stores software1980, images, and video that can, for example, be used withimplementations of technologies described herein. A computingenvironment may have additional features. For example, the computingenvironment 1900 includes storage 1940, one or more input devices 1950,one or more output devices 1960, and one or more communicationconnections 1970. An interconnection mechanism (not shown) such as abus, a controller, or a network, interconnects the components of thecomputing environment 1900. Typically, operating system software (notshown) provides an operating environment for other software executing inthe computing environment 1900, and coordinates activities of thecomponents of the computing environment 1900.

The storage 1940 may be removable or non-removable, and includesmagnetic disks, magnetic tapes or cassettes, CD-ROMs, CD-RWs, DVDs, orany other medium which can be used to store information and that can beaccessed within the computing environment 1900. The storage 1940 storesinstructions for the software 1980, which can be used to implementtechnologies described herein.

The input device(s) 1950 may be a touch input device, such as akeyboard, keypad, mouse, touch screen display, pen, or trackball, avoice input device, a scanning device, or another device, that providesinput to the computing environment 1900. For audio, the input device(s)1950 may be a sound card or similar device that accepts audio input inanalog or digital form, or a CD-ROM reader that provides audio samplesto the computing environment 1900. The output device(s) 1960 may be adisplay, printer, speaker, CD-writer, or another device that providesoutput from the computing environment 1900.

The communication connection(s) 1970 enable communication over acommunication medium (e.g., a connecting network) to another computingentity. The communication medium conveys information such ascomputer-executable instructions, compressed graphics information,video, or other data in a modulated data signal. The communicationconnection(s) 1970 are not limited to wired connections (e.g., megabitor gigabit Ethernet, Infiniband, Fibre Channel over electrical or fiberoptic connections) but also include wireless technologies (e.g., RFconnections via Bluetooth, WiFi (IEEE 802.11a/b/n), WiMax, cellular,satellite, laser, infrared) and other suitable communication connectionsfor providing a network connection for the disclosed network dataoperations. In a virtual host environment, the communication(s)connections can be a virtualized network connection provided by thevirtual host.

Some embodiments of the disclosed methods can be performed usingcomputer-executable instructions implementing all or a portion of thedisclosed technology in a computing cloud 1990. For example, disclosedcompilers and/or block-based-processor servers are located in thecomputing environment 1930, or the disclosed compilers can be executedon servers located in the computing cloud 1990. In some examples, thedisclosed compilers execute on traditional central processing units(e.g., RISC or CISC processors).

Computer-readable media are any available media that can be accessedwithin a computing environment 1900. By way of example, and notlimitation, with the computing environment 1900, computer-readable mediainclude memory 1920 and/or storage 1940. As should be readilyunderstood, the term computer-readable storage media includes the mediafor data storage such as memory 1920 and storage 1940, and nottransmission media such as modulated data signals.

XX. Additional Examples of the Disclosed Technology

Additional examples of the disclosed subject matter are discussed hereinin accordance with the examples discussed above.

In some examples of the disclosed technology, an apparatus includes aprocessor having two or more execution lanes. The processor can includea data cache, which is coupled to memory, a wide memory load circuitthat concurrently loads two or more words from a cache line of the datacache, and a writeback circuit situated to send a respective word of theconcurrently-loaded words to a selected execution lane of the processor.The processor can execute instructions encoded in one or more differentinstruction sets, including CISC, RISC, block-based, DSP, or other ISA.In some examples, the memory coupled to the processor is on the sameintegrated circuit. In other examples, the memory is situated on adifferent integrated circuit and coupled to the processor usinginterconnect (e.g., in a multi-chip module, with an interposer, or on aprinted circuit board). In some examples, the processor is an ExplicitData Graph Execution (EDGE) processor. In some examples, the processoris a neural network processor.

In some examples of the apparatus, the processor writeback circuit isfurther situated to send at least one respective word to an operandbuffer for the selected execution lane. In some examples, the writebackcircuit is further situated to send the respective word to bypass anoperand buffer by sending the respective word directly to an executionunit of the selected execution lane. In some examples, the respectiveword bypasses the operand buffer and is not stored in an operand buffer.In some examples, the writeback circuit includes interconnectconfigurable to, during a particular clock cycle, select and send eitherwords from the cache line of the data cache or words from the executionlanes to an operand buffer. In some examples, a different word of thecache line is sent to a respective each one of the execution lanes. Theapparatus of claim 1, wherein the processor is an Explicit Data GraphExecution (EDGE) processor or a neural network processor.

In some examples, the apparatus further includes a sharding circuitcoupled to the wide memory load circuit, the sharding circuit beingconfigured to select individual words from the cache line and to sendeach of the selected words to a selected writeback channel of theprocessor. In some examples, the sharding circuit is configured toreorder and send a respective word from the writeback circuit to arespective one of the selected execution lanes. In some examples, thesharding circuit is configured to reorder the respective words byperforming at least one of the following operations: shift, rotate,reverse, move, swap, transpose, replicate, permute, extract, or extend.In some examples, the sharding circuit can perform arithmetic or logicaloperations. In some examples, one or more of the input words to thesharding circuit are replicated and so one or more of the input words isnot output by the sharding circuit. In some examples, two or more of theoperations can be performed in combination with each other. In someexamples, an operation is performed on one or more but not all words ofthe input to the sharding circuit, and thus only a subset of theprocessed input words are output.

In some examples, the respective word includes packed data and theselected execution lane is configured to perform a single instructionmultiple data (SIMD) operation with the respective word, the operationbeing performed separately for each of two or more portions of therespective word. For example, the word can include two, three, four,six, eight, 16, 32, or other number of portions of packed operands thatare operated on independently of one another.

In some examples of the disclosed technology, a method of operating aprocessor having a plurality of execution lanes includes concurrentlyloading a plurality of two or more words from a single read port of adata cache and sending a selected word of the plurality of words to aselected one of the execution lanes of the processor. The processor canexecute instructions encoded in one or more different instruction sets,including CISC, RISC, block-based, DSP, or other ISA. In some examples,memory coupled to the processor is on the same integrated circuit. Inother examples, the memory is situated on a different integrated circuitand coupled to the processor using interconnect (e.g., in a multi-chipmodule, with an interposer, or on a printed circuit board). In someexamples, the processor is an Explicit Data Graph Execution (EDGE)processor. In some examples, the processor is a neural networkprocessor.

In some examples, the method further includes sending a selected eachword of the plurality of words to a respective selected one of theexecution lanes of the processor. For example, each of the plurality ofwords can be sent to a different respective selected one of theprocessor execution lanes. In some examples, the selected word is sentto the selected one of the execution lanes via a writeback path, thewriteback path being adapted to select and send at least an executionlane output or the selected word to the selected execution lane.

In some examples, the selected word is sent to an operand buffer. Insome examples, the selected word bypasses an operand buffer and is sentdirectly to execution resources of the selected execution lane.

In some examples, the method further includes receiving the selectedword via a writeback circuit, and, with the selected execution lane,multiplying the received word by an operand output, thereby producing aproduct.

In some examples of the method, the selected word is a first selectedword and the plurality of words is a first plurality of words, and themethod further includes concurrently loading a second plurality of twoor more words from a single read port of a data cache and adding asecond, selected word of the second plurality of words to the product.In some examples, the method further includes not storing the firstselected word, the second selected word, or the first and secondselected words in an operand buffer.

In some examples, the method further includes performing a singleinstruction multiple data (SIMD) operation for at least two separateportions of the selected word. In some examples, the processor is anexplicit data graph execution (EDGE) processor. In some examples, theprocessor is neural network processor. The processor can executeinstructions encoded in one or more different instruction sets,including CISC, RISC, block-based, DSP, or other ISA.

In some examples, one or more computer-readable storage media storingcomputer-readable instructions that when executed by a processor, causethe processor to perform any of the disclosed methods. In some examples,the processor is an explicit data graph execution (EDGE) processor. Insome examples, the processor is neural network processor. The processorcan execute instructions encoded in one or more different instructionsets, including CISC, RISC, block-based, DSP, or other ISA. For example,the computer-readable storage media can cause the processor to perform amethod include identifying at least one vector operation in code for atleast one instruction block and emitting object code, intermediatelanguage code, or assembly code for the at least one instruction blockthat, when the code is executed by a processor, causes the processor toperform any one of the disclosed methods. In some examples, the objectcode includes at least one instruction encoded to indicate that theplurality of words is to be loaded and sent to the selected executionlanes.

In some examples, the code is not specifically encoded to indicate thatthe plurality of words is to be loaded and sent to the selectedexecution lanes, and wherein the processor is configured to determinethat the plurality of words is to be loaded and sent to the selectedexecution lanes.

In some examples, a method of operating a processor includes receivingobject code for at least one instruction block, scheduling one or moreoperations specified in an instruction block to be executed by two ormore execution lanes of a processor core, and executing the scheduledoperations by processor. In some examples, the executing includesperforming a memory operation for a cache line of a data cache, each ofplural words of the cache line memory operation being associated withone of the execution lanes of the process core.

In some examples, the memory operation is a load operation, and theperforming the memory operation includes sending each of respectiveplural words to a different execution lane of the processor. In someexamples, the memory operation is a store operation, and wherein theperforming the memory operation comprises sending each of respectiveplural words from its associated execution lane to the same cache lineof the data cache for writing to memory coupled to the processor. Insome examples, performing the memory operation comprises performing asharding operation for the plural words after loading from or beforestoring words in the data cache. In some examples, the schedulingcomprises assigning one of the execution lanes as a leader lane, and theremaining execution lanes concurrently follow the leader lane whenexecuting the scheduled operations. In some examples, the schedulingincludes performing the memory operation for all of the execution lanesconcurrently, and the executing the scheduled operations is performed ina different clock cycle for at least one of the execution lanes thananother one of the execution lanes.

In some examples, the scheduled operations comprise at least one or moreof the following: a multiplication inner loop, a dot product operation,a cross product operation, a multiply-add operation, a matrix arithmeticoperation, or a vector arithmetic operation. In some examples, themethod includes evaluating a neural network by performing the schedulingand executing operations. In some examples, the executing includes notwriting back values produced by the memory operation to operand buffersof the processor.

In some examples of the method, the memory operation is a first loadoperation and the executing the scheduled operations further includesperforming a second load operation, where each of the plural words forthe first load operation is stored in an operand buffer and where eachof the plural words for the second load operation is not stored in theoperand buffer but is immediately combined with a result calculatedbased on the plural words stored in the operand buffer.

In view of the many possible embodiments to which the principles of thedisclosed subject matter may be applied, it should be recognized thatthe illustrated embodiments are only preferred examples and should notbe taken as limiting the scope of the claims to those preferredexamples. Rather, the scope of the claimed subject matter is defined bythe following claims. We therefore claim as our invention all that comeswithin the scope of these claims and their equivalents.

What is claimed is:
 1. An apparatus comprising a processor having two ormore execution lanes, the processor comprising: a data cache coupled tomemory; a wide memory load circuit that concurrently loads two or morewords from a cache line of the data cache; and a writeback circuitsituated to send a respective word of the concurrently-loaded words to aselected execution lane of the processor, the writeback circuitincluding interconnect configurable to, during a particular clock cycle,select and send either words from the cache line of the data cache orwords from the execution lanes to an operand buffer.
 2. The apparatus ofclaim 1, wherein: the writeback circuit is further situated to send therespective word to an operand buffer for the selected execution lane. 3.The apparatus of claim 1, wherein: the writeback circuit is furthersituated to send the respective word to bypass an operand buffer bysending the respective word directly to an execution unit of theselected execution lane.
 4. The apparatus of claim 3, wherein therespective word is not stored in an operand buffer.
 5. The apparatus ofclaim 1, wherein: the selected execution lane is configured to perform asingle instruction multiple data (SIMD) operation with the respectiveword, the operation being performed separately for each of two or moreportions of the respective word.
 6. The apparatus of claim 1, whereinthe writeback circuit comprises electrical or photonic interconnectwires and selection logic comprising as least one of a logicmultiplexer, pass-gate multiplexer, transmission gate multiplexer, ortri-state bus.
 7. An apparatus comprising a processor having two or moreexecution lanes, the processor comprising: a data cache coupled tomemory; a wide memory load circuit that concurrently loads two or morewords from a cache line of the data cache; a writeback circuit situatedto send a respective word of the concurrently-loaded words to a selectedexecution lane of the processor; and a sharding circuit coupled to thewide memory load circuit, the sharding circuit being configured toselect individual words from the cache line and to send each of theselected words to a selected writeback channel of the processor.
 8. Theapparatus of claim 7, wherein the writeback circuit is further situatedto send the respective word to bypass an operand buffer by sending therespective word directly to an execution unit of the selected executionlane.
 9. An apparatus comprising a processor having two or moreexecution lanes, the processor comprising: a data cache coupled tomemory; a wide memory load circuit that concurrently loads two or morewords from a cache line of the data cache; a writeback circuit situatedto send a respective word of the concurrently-loaded words to a selectedexecution lane of the processor; and a sharding circuit configured toreorder and send a respective word from the writeback circuit to arespective one of the selected execution lanes.
 10. The apparatus ofclaim 9, wherein: the sharding circuit is configured to reorder therespective word by performing at least one of the following operations:shift, rotate, reverse, move, swap, transpose, replicate, extract, orextend.
 11. The apparatus of claim 9, wherein the writeback circuit isfurther situated to send the respective word to bypass an operand bufferby sending the respective word directly to an execution unit of theselected execution lane.
 12. A method of operating a processor having aplurality of execution lanes, the method comprising: concurrentlyloading a plurality of two or more words from a single read port of adata cache; sending a selected word of the plurality of words to aselected one of the execution lanes of the processor; receiving theselected word via a writeback circuit; and with the selected executionlane, multiplying the received word by an operand output, therebyproducing a product.
 13. The method of claim 12, wherein: the selectedword is sent to the selected one of the execution lanes via a writebackpath, the writeback path being adapted to select and send at least anexecution lane output or the selected word to the selected executionlane.
 14. The method of claim 12, wherein: the selected word bypasses anoperand buffer and is sent directly to execution resources of theselected execution lane.
 15. The method of claim 12, wherein theselected word is a first selected word and wherein the plurality ofwords is a first plurality of words, further comprising: concurrentlyloading a second plurality of two or more words from a single read portof a data cache; and adding a second, selected word of the secondplurality of words to the product.
 16. One or more computer-readablestorage media storing computer-readable instructions that when executedby a processor, cause the processor to perform a method, the methodcomprising: identifying at least one vector operation in code for atleast one instruction block; and emitting object code for the at leastone instruction block that, when the object code is executed by aprocessor, causes the processor executing the object code to perform amethod, the method comprising: concurrently loading a plurality of twoor more words from a single read port of a data cache, sending aselected word of the plurality of words to a selected one of theexecution lanes of the processor, receiving the selected word via awriteback circuit, and with the selected execution lane, multiplying thereceived word by an operand output, thereby producing a product.
 17. Thecomputer-readable storage media of claim 16, wherein the object codeincludes at least one instruction encoded to indicate that the pluralityof words is to be loaded and sent to the selected execution lanes.
 18. Amethod of operating a processor, comprising: with a wide memory loadcircuit, concurrently loading two or more words from a cache line of adata cache coupled to memory; and with a writeback circuit, sending arespective word of the concurrently-loaded words to a selected executionlane of the processor; and with a sharding circuit coupled to the widememory load circuit, selecting individual words from the cache line andsending each of the selected words to a selected writeback channel ofthe processor.
 19. The method of claim 18, further comprising: with thewriteback circuit, sending the respective word to an operand buffer forthe selected execution lane.
 20. The method of claim 18, furthercomprising: with the writeback circuit, sending the respective word tobypass an operand buffer by sending the respective word directly to anexecution unit of the selected execution lane.